Varied frame rate video

Abstract

A method and apparatus wherein raw video and audio are captured and digitized and stored at a frame rate different from the playback stand frame rate. The audio and the video are separated, the video as a frame and the audio as a data stream wherein there are time links to the video frame. The playback entails multiplexing the video and the audio, and where the multiplexer is operating at the standard frame rate synchronization is not maintained. The present invention discloses modifications of the audio header and/or data to accommodate the differences in the multiplexing frame rate and the original capture frame rate. If the originating frame rate is one half the standard then the audio header information is changed to indicate that twice as much audio information exists, whereupon the multiplexer will take the video frames and properly multiplex the proper and therefore synchronized audio data. For example, the existence of 150 video frames originally taken at 15 fps or 10 seconds worth of video, causes the multiplexer and the associated software to presume that the 150 frames were taken at 30 frames per second and the 5 seconds worth of audio was required. The header is changed to indicate there is half as much audio or five seconds worth, which is the correct value. The resulting multiplexing of video and audio is in synchronization.

What is claimed is: 
     
       1. A method for multiplexing a stored digital video file and a stored digital audio file, or a combined video/audio file, where the stored video and audio files are sampled, recorded and digitized at a first frame rate, FR1, but where the multiplexing assumes a second frame rate, FR2, and where said multiplexing preserves the video and audio synchronization, comprising the steps of: storing said digital audio file with first control bits associated with said audio file which relate to a digitizing process having a value compliant with FR2,   multiplying the value of said first control bits by FR2/FR1 forming second control bits,   replacing said first control bits by said second control bits,   notifying said multiplexing and where said audio control bits are located,   multiplexing said stored digital video file and said stored digital audio file containing said second control bits.   
     
     
       2. The method of claim 1 wherein FR2 is evenly divisible by FR1. 
     
     
       3. The method of claim 1 wherein the video and audio are digitized into files and multiplexed together for playback under one of the MPEG standards. 
     
     
       4. The method of claim 3 wherein the MPEG standard is MPEG-1, and said first and second control bits comprise sampling rate and average bytes per second information. 
     
     
       5. The method of claim 1 wherein said FR1 is 15 or 7.5 frames per second, and said FR2 is 30 frames per second. 
     
     
       6. The method of claim 1 wherein said FR1 is 12 or 6 frames per second, and said FR2 is 24 frames per second. 
     
     
       7. A method for multiplexing a stored digital video file and a stored digital audio file, where the stored video and audio files are recorded and digitized at a first frame rate, FR1, but where the multiplexing assumes a second frame rate, FR2, and where said multiplexing preserves the video and audio synchronization, comprising the steps of: storing said digital audio file at a first location where the actual data packets start,   divide FR2/FR1 forming a first factor, N,   forming a second stored digital audio file by taking every Nth packet of the first stored digital audio file,   multiplexing said stored digital video file and said second stored digital audio file.   
     
     
       8. A method as in claim 7 wherein N equal 2 and every second packet is taken to form the second stored digital audio file. 
     
     
       9. The method of claim 7 wherein N equals 4 and every fourth packet is taken to form the second stored digital audio file. 
     
     
       10. Computer and associated apparatus for multiplexing a stored digital video file and a stored digital audio file, where the stored video and audio files are sampled, recorded and digitized at a first frame rate, FR1, but where the multiplexing assumes a second frame rate, FR2, and where said multiplexing preserves the video and audio synchronization, comprising: means for storing said digital audio file with first control bits associated with said audio file which relate to a digitizing process having a value compliant with FR2,   means for multiplying the value of said first control bits by FR2/FR1 forming second control bits,   means for replacing said first control by said second control bits,   means for notifying said multiplexing and where said audio control bits are located, and   a multiplexer wherein said stored digital video file and said stored digital audio file containing said second control bits are combined producing a synchronized video/audio data stream.   
     
     
       11. Apparatus as in claim 10 further comprising means for formatting said audio and video files into MPEG-1 files, and said first and second control bits comprise sampling rate and average bytes per second information. 
     
     
       12. Computer and associated hardware and software for multiplexing a stored digital video file and a stored digital audio file, where the stored video and audio files are recorded and digitized at a first frame rate, FR1, but where the multiplexing assumes a second frame rate, FR2, and where said multiplexing preserves the video and audio synchronization, comprising: means for storing said digital audio file at a first location where the actual data packets start,   means for dividing FR2/FR1 forming a first factor, N,   means for forming a second stored digital audio file by taking every Nth packet of the first stored digital audio file,   a multiplexer wherein said stored digital video file and said second stored digital audio file are combined.   
     
     
       13. Apparatus as in claim 12 further comprising means for formatting said audio and video files into MPEG-1 files, and N is a whole number.